1. Field of the Invention
The present invention relates to a ceramic powder that contains barium titanate having a perovskite structure, and a multi-layer ceramic capacitor (MLCC) obtained by using said ceramic powder, particularly useful for a MLCC using a thin-layer dielectric layer.
2. Description of the Related Art
Multi-layer ceramic capacitors (MLCCs) are used in various electronic devices including mobile devices and communications devices.
The trend for smaller, higher-performance MLCCs and other electronic components has been prominent in recent years and, in the case of MLCCs, for example, these capacitors are becoming significantly smaller and larger in capacity. The capacity of a MLCC is proportional to the number of dielectric layers constituting the base material of the MLCC, and inversely proportional to the thickness per dielectric layer, and consequently it is desirable to keep the dielectric layer thin, such as 1 μm or less, and increase the number of layers.
For the material ceramic powder with which to form such dielectric layer, barium titanate powder having a perovskite structure is widely used.
To ensure performance and reliability, and also from the viewpoint of physical characteristics, it is important that the barium titanate powder consist of fine particles so as to make the aforementioned dielectric layer thinner.
Here, one proposed method to synthesize a barium titanate compound suitable for making the dielectric layer thinner is to crush and mix with an organic solvent a powder mixture containing barium carbonate powder and titanium dioxide powder, and then sinter the crushed and mixed powder mixture to obtain a powder of barium titanate compound (Patent Literature 1).
According to Patent Literature 1, the powder of barium titanate compound obtained by the method described therein has an average particle size of 100 nm or smaller, contains twin defects in at least 10% of the particles, and its standard deviation of particle distribution is 20 or smaller. It is also described that, by using this powder, variation of surface roughness can be suppressed and consequently the shorting rate and insulation resistance failure of the MLCC can be suppressed.